Ответы и объяснения

1. must
2. must 
3. can't
4. can't
5. must
6. must

2. She can't be old enough.
3. He can't be very intelligent.
4. She must be hungry.
5. She can't be an Italian (Если мы говорим о той женщине, что слева))) (Или She must be an Italian - если о той, что справа)

I haven't eaten for six hours. - You must be hungry.
I have lost the CDs I bought yesterday. - You must be sad.
Linda told me she's broken my MP3 player. - You must be angry.
I'd like another burger. - You've already eaten five. You can't be hungry.
Can you give me another sweater, please? - You've already got three. You can't be cold.